The present invention relates to a turbine engine blade, and more particularly to a blade of a rotor wheel of a turbine engine.
The invention relates more particularly to a rotor wheel of a low-pressure gas turbine of the type used in an aviation turbojet.
Conventionally, a turbojet has a plurality of nozzle stages, e.g. four stages. Each stage comprises a stationary nozzle forming a stator, and a rotor wheel, the nozzle and the wheel each having a plurality of vanes or blades organized radially relative to the longitudinal axis of the turbojet, which is the axis of rotation of the wheel.
Below, it is assumed that the axial direction X is the direction of the axis of rotation of the wheel on which the blade is to be mounted, that the radial direction Z is the height direction of the blade between its root and its tip, and that the tangential direction Y is the direction perpendicular to the axial and radial directions.
The invention applies more particularly to the rotor wheels of the first and second stages of a four-stage turbojet.
The blades of a turbine engine are subjected to high speeds of rotation. The main stream that provides propulsion is disturbed by secondary phenomena, in particular due to turbulence generated by passage vortices and by corner vortices. These vortices are present on the suction side of a blade, respectively in the main portion and in the region of its trailing edge. They originate from the stream of gas at the wall, of an intensity that depends on the pressure gradient between the pressure side and the suction side.
Such vortices give rise to sound nuisance and to vibration that it is desired to reduce. Furthermore, they give rise locally to pressure gradients that can reduce propulsive efficiency and constitute an additional source of mechanical fatigue.
Attempts have already been made to reduce those secondary phenomena, for example by fitting blades with special platforms at their roots and/or at their tips. Those solutions present a certain amount of effectiveness, but when they are employed, secondary phenomena continue to exist, even if they are reduced.
The applicant has directed its attention to the particular shape of the blade.
Its research has led it to find that the variation in the curve plotting deviation between the root and the tip of the blade can be optimized in such a manner as to reduce the above-mentioned secondary phenomena.